Browsing by Author "Schmidt, K."

Now showing 1 - 11 of 11

Citation - Scopus: 7
Abstraction-Based Control for Not Necessarily Closed Behaviours
(IFAC Secretariat, 2011) Moor, T.; Schmidt, K.; Wittmann, T.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
This paper addresses abstraction-based supervisory control for plant and specification behaviours that are not necessarily ω-closed, i.e. plant behaviours that exhibit eventuality properties and specifications that impose eventuality properties on the closed loop. Technically, the core idea is to combine results from previous work on abstraction-based supervision of input-output behaviours with results on supervisory control of ω-languages. As our main result, we identify a controllability condition for the plant, that ensures a nonblocking closed-loop behaviour with a controller that has been obtained for a plant abstraction. © 2011 IFAC.
Citation - WoS: 12
Citation - Scopus: 17
Abstraction-Based Verification of Codiagnosability for Discrete Event Systems
(Pergamon-elsevier Science Ltd, 2010) Schmidt, K.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this paper, we investigate the verification of codiagnosability for discrete event systems (DES). That is, it is desired to ascertain if the occurrence of system faults can be detected based on the information of multiple local sites that partially observe the overall DES. As an improvement of existing codiagnosability tests that resort to the original DES with a potentially computationally infeasible state space, we propose a method that employs an abstracted system model on a smaller state space for the codiagnosability verification. Furthermore, we show that this abstraction can be computed without explicitly evaluating the state space of the original model in the practical case where the DES is composed of multiple subsystems. (c) 2010 Elsevier Ltd. All rights reserved.
Citation - Scopus: 12
Applied Supervisory Control for a Flexible Manufacturing System
(IFAC Secretariat, 2010) Moor, T.; Schmidt, K.; Perk, S.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
This paper presents a case study in the design and implementation of a discrete event system (DES) of real-world complexity. Our DES plant is a flexible manufacturing system (FMS) laboratory model that consists of 29 interacting components and is controlled via 107 digital signals. Regarding controller design, we apply a hierarchical and decentralised synthesis method from earlier work in order to achieve nonblocking and safe closed-loop behaviour. Regarding implementation, we discuss how digital signals translate to discrete events from a practical point of view, including timing issues. The paper demonstrates how both, design and implementation, are supported by the open-source software tool libFAUDES.
Computation of Projections for the Abstraction-Based Diagnosability Verification
(IFAC Secretariat, 2010) Schmidt, K.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The verification of language-diagnosability (LD) for discrete event systems (DES) generally requires the explicit evaluation of the overall system model which is infeasible for practical systems. In order to circumvent this problem, our previous work proposes the abstraction-based LD verification using natural projections that fulfill the loop-preserving observer (LPO) property. In this paper, we develop algorithms for the verification and computation of such natural projections. We first present a polynomial-time algorithm that allows to test if a given natural projection is a loop-preserving observer. Then, we show that, in case the LPO property is violated, finding a minimal extension of the projection alphabet such that the LPO condition holds is NP-hard. Finally, we adapt a polynomial-time heuristic algorithm by Feng and Wonham for the efficient computation of loop-preserving observers.
Dinamik Dağıtık Gerçek Zamanlı Endüstriyel İletişim Protokolü (d2gep) Gerçekleştirimi
(2012) Gözcü, A. K.; Turan, U.; Schmidt, E. G.; Schmidt, K.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Citation - Scopus: 2
An Experimental Study of the Flexray Dynamic Segment
(IFAC Secretariat, 2010) Schmidt, K.; Schmidt, E.G.; Demirci, A.; Yürüklü, E.; Karakaya, U.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
It is expected that the time-triggered FlexRay bus will replace the event-triggered Controller Area Network (CAN) for the high-speed in-vehicle communication in future automobiles. To this end, FlexRay provides a static segment for the transmission of periodic messages and a dynamic segment that is suitable for exchanging event-based (sporadic) messages. In this paper, we experimentally evaluate the operation of the FlexRay dynamic segment. In particular, we study how the maximum and average message delays are affected if the length of the dynamic segment, the message payload, the utilization of the dynamic segment and the priority assignment changes. Our experiments are carried out on a FlexRay network with 6 nodes. © 2010 IFAC.
Citation - Scopus: 1
Fuzzy Hybrid Systems Modeling With Application in Decision Making and Control
(2012) Boutalis, Y.; Moor, T.; Schmidt, K.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Hybrid Systems are systems containing both discrete event and continuous variable components. Many recent contributions address crisp situations, where ambiguity or subjectivity in the measured data is absent. In this paper, we propose Fuzzy Hybrid Systems to account for inaccurate measurements and uncertain dynamics. We present a strategy to determine the most appropriate control actions in a sampled data setting. The proposed approach is based on three basic steps that are performed in each sampling period. First, the current discrete fuzzy state of the system is determined by a sensor evaluation. Next, the future discrete fuzzy state is predicted for the possible control actions and the best action, in respect to desired continuous states, is selected. Finally, the decision is cross-evaluated by a limited horizon prediction of the continuous system variables. The proposed method is explained and demonstrated for a variation of the a well-known two-tank scenario. © 2012 IEEE.
Hierarchical Multitasking Control of Discrete Event Systems: Computation of Projections and Maximal Permissiveness
(IFAC Secretariat, 2010) Cury, J.E.R.; Schmidt, K.; De Queiroz, M.H.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
This paper extends previous results on the hierarchical and decentralized control of multitasking discrete event systems (MTDES). Colored observers, a generalization of the observer property, together with local control consistency, allow to derive sufficient conditions for synthesizing modular and hierarchical control that are both strongly nonblocking (SNB) and maximally permissive. A polynomial procedure to verify if a projection fulfills the above properties is proposed and in the case they fail for a given projection an algorithm is proposed to find an extension of the set of events to be projected, in order to fulfill the sufficient conditions for SNB and maximally permissive hierarchical control.
Citation - Scopus: 11
A Longest-Path Problem for Evaluating the Worst-Case Packet Delay of Switched Ethernet
(2010) Schmidt, K.; Schmidt, E.G.; 17337; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In the recent years, the use of real-time Ethernet protocols becomes more and more relevant for time-critical networked industrial applications. In this context, this paper presents a method to compute the worst-case packet delays on switched Ethernet. Based on an evaluation of the packet delays at each switch port and the network topology, we construct a weighted directed graph that allows to find the worst-case end-toend packet delay by solving a conventional longest-path problem. © 2010 IEEE.
Citation - Scopus: 8
Multi-Objective Decision Making Using Fuzzy Discrete Event Systems: a Mobile Robot Example
(2010) Boutalis, Y.; Schmidt, K.; 06.08. Mekatronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this paper, we propose an approach for the multi-objective control of sampled data systems that can be modeled as fuzzy discrete event systems (FDES). In our work, the choice of a "fuzzy" system representation is justified by the assumption of a controller realization that depends on various potentially imprecise sensor measurements. Our approach consists of three basic steps that are performed in each sampling instant. First, the current fuzzy state of the system is determined by a sensor evaluation. Second, the future fuzzy state is predicted for the possible control actions, and finally, a particular multi-objective weighting strategy allows to determine the control action to be applied. We demonstrate the features of our method by a mobile robot example. © 2010 IEEE.
Citation - Scopus: 19
Performance Evaluation of Flexray/Can Networks Interconnected by a Gateway
(2010) Schmidt, E.G.; Alkan, M.; Schmidt, K.; Yürüklü, E.; Karakaya, U.; 03.05. Siyaset Bilimi ve Uluslararası İlişkiler; 06.08. Mekatronik Mühendisliği; 03. İktisadi ve İdari Birimler Fakültesi; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The coexistence of both CAN and FlexRay networks in contemporary and future automobiles necessitates the use of FlexRay/CAN gateways that support the timely data exchange among the different networks. In this paper, we report on the implementation of such FlexRay/CAN gateway. Moreover, for the first time, we investigate appropriate network and gateway configurations that are beneficial for the overall network performance in the sense of small delays of gateway messages. © 2010 IEEE.